Generally, vehicle sound, such as a warning sound, a guidance voice, and the like is output through internal or external speaker signals output from a built-in amplifier of a cluster. The signals output through the speaker are prevented from being output at a certain level or higher through a process of advance tuning the signal having a certain level.
However, if the sound simultaneously generated in multi-channels is output through the speaker, it is possible to exceed the output level limit of the speaker, or an interference between the sounds simultaneously generated in the multi-channels may occur, generating a distorted output through the speaker, thereby causing discomfort to a driver.
In addition, although a warning sound or alarm has a main frequency which is simple and fixed, when the warning sound or alarm is combined with a guidance voice it is possible to temporarily exceed the output range of the speaker because the combined sound consists of various frequency bands.